Re: [PATCH] soc_camera: fix compiler warning

[Hans Verkuil <hverkuil@xs4all.nl>]

Hi Guennadi,

On 07/26/2013 01:26 PM, Guennadi Liakhovetski wrote:
> Hi Hans
> 
> Thanks for the patch.
> 
> On Thu, 25 Jul 2013, Hans Verkuil wrote:
> 
>>
>> media_build/v4l/soc_camera.c: In function 'soc_camera_host_register':
>> media_build/v4l/soc_camera.c:1513:10: warning: 'sasd' may be used uninitialized in this function [-Wmaybe-uninitialized]
>>   snprintf(clk_name, sizeof(clk_name), "%d-%04x",
>>           ^
>> media_build/v4l/soc_camera.c:1464:34: note: 'sasd' was declared here
>>   struct soc_camera_async_subdev *sasd;
>>                                   ^
> 
> Heh, cool... You did report a similar warning earlier, for which I cooked 
> up a patch "[media] V4L2: soc-camera: fix uninitialised use compiler 
> warning" and IIRC you reported that with that patch the warning 
> disappeared... How come we've got another one now? Have you updated your 
> compiler again or what can be the reason?

It worked, but only for i686. The x86_64 compiler (exactly the same gcc version
BTW) still couldn't understand that it really was initialized. See the build
logs from the past few weeks.

> In principle I have nothing against this patch, just wondering where 
> you're getting your compilers from ;-)

Well, the compiler is just downloaded from gnu.org and regularly updated when
a new version is released.

The problem is not with the current git build, but with the compatibility builds.
As far as I can tell different kernel versions may turn on or off different
compiler warnings, so compiling for different kernels gives different results.

>> By changing the type of 'i' to unsigned and changing a condition we finally
>> convince the compiler that sasd is really initialized.
>>
>> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
> 
> I haven't got any more 3.11 fixed in my queue and we have to push this 
> before -rc3 / rc4 ;) So, if you prefer, feel free to take it via your tree 
> with my
> 
> Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>

This is just for 3.12, there is no need to go to 3.11 for this since the warning
doesn't appear when compiling 3.11.

Do you still want me to take it, or do you prefer to queue it for 3.12 yourself?
For the record, I expect to post a pull request for 3.12 today or Monday at the
latest, so it's no problem for me.

	Hans

> 
> Thanks
> Guennadi
> 
>> ---
>>  drivers/media/platform/soc_camera/soc_camera.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/media/platform/soc_camera/soc_camera.c b/drivers/media/platform/soc_camera/soc_camera.c
>> index 2dd0e52..ed7a99f 100644
>> --- a/drivers/media/platform/soc_camera/soc_camera.c
>> +++ b/drivers/media/platform/soc_camera/soc_camera.c
>> @@ -1466,7 +1466,8 @@ static int scan_async_group(struct soc_camera_host *ici,
>>  	struct soc_camera_device *icd;
>>  	struct soc_camera_desc sdesc = {.host_desc.bus_id = ici->nr,};
>>  	char clk_name[V4L2_SUBDEV_NAME_SIZE];
>> -	int ret, i;
>> +	unsigned int i;
>> +	int ret;
>>  
>>  	/* First look for a sensor */
>>  	for (i = 0; i < size; i++) {
>> @@ -1475,7 +1476,7 @@ static int scan_async_group(struct soc_camera_host *ici,
>>  			break;
>>  	}
>>  
>> -	if (i == size || asd[i]->bus_type != V4L2_ASYNC_BUS_I2C) {
>> +	if (i >= size || asd[i]->bus_type != V4L2_ASYNC_BUS_I2C) {
>>  		/* All useless */
>>  		dev_err(ici->v4l2_dev.dev, "No I2C data source found!\n");
>>  		return -ENODEV;
>> -- 
>> 1.8.3.2
>>
> 
> ---
> Guennadi Liakhovetski, Ph.D.
> Freelance Open-Source Software Developer
> http://www.open-technology.de/
>